It is known in the art to prepare photosensitive silver halide grains in the presence of ammonia. For example, on page 61 of Photographic Emulsion Chemistry, G. F. Duffin, The Focal Press, New York, 1966, it is stated that ammonia is generally introduced into the silver halide precipitation procedure either in the silver solution or alternatively in the halide gelation solution and/or in the added halide in a double jet procedure. Examples of such procedures also appear in the patent art.
U.S. Pat. Nos. 2,005,837; 2,184,013; 2,576,850; 3,598,593 and 3,647,458 describe various methods for preparation of silver halide grains which employ ammoniacal silver nitrate solutions.
U.S. Pat. No. 4,259,438, issued Mar. 31, 1981, is directed to a method for forming photosensitive silver halide grains which comprises the steps of simultaneously introducing into an aqueous solution of gelatin and ammonium halide, an ammoniacal solution of silver nitrate and a second solution of an ammonium halide. More specifically, silver halide grains substantially uniform in size, having a 0.5-10% iodide content and wherein the core is iodide-rich compared to the rest of the grain are prepared by simultaneously introducing into an aqueous solution of gelatin, ammonium bromide and a water-soluble iodide salt, an ammoniacal solution of silver nitrate and a solution of ammonium bromide or chloride.
On page 61 of Duffin, referred to above, it is also stated that:
"Iodobromide emulsions usually contain between 20% and 250% excess bromide during precipitating and ripening: those for negative purposes commonly containing the highest amounts while X-ray emulsions have the lowest."